Breathing circuits have been used in the anesthesia field for many years to provide a vehicle for transferring anesthesia gas from an anesthesia machine to a patient, and to transfer exhaled gas from the patient to the anesthesia machine. Currently, two primary types of breathing circuits are used. The first type is known as a dual-limb circuit. Such a device includes an expiratory tube and an inspiratory tube that are usually connected to a `Y` connector. The `Y` connector is then coupled, at its patient end, to an anesthesia face mask or an endotracheal tube. The machine end of the inspiratory tube is coupled to the inspiratory port of either an anesthesia machine, or to a carbon dioxide absorber that is attached to an anesthesia machine. The machine end of the expiratory tube is attached to either the anesthesia machine, or to a carbon dioxide absorber attached to an anesthesia machine. An example of a carbon dioxide absorber is shown in Komesaroff U.S. Pat. No. 5,666,669, that issued on Oct. 22, 1996.
The other type of circuit is a "unilimb" circuit. An example of a unilimb circuit is shown in Leagre and Burrow U.S. Pat. No. 5,404,873 and Fukunaga U.S. Pat. No. 4,265,235. A unilimb breathing circuit includes an expiratory tube and an inspiratory tube that are coupled in a coaxial relation. Usually, the inspiratory tube is disposed within the interior of the expiratory tube. A patient end connector is provided for coupling the patient end of the unilimb breathing circuit to either an anesthesia face mask or an endotracheal tube. The machine end of the unilimb circuit contains a coupler having an inspiratory coupler and a separate, expiratory coupler. The inspiratory coupler is coupled to the inspiratory port of a carbon dioxide absorber or anesthesia machine, and the expiratory coupler is coupled to the expiratory port of the anesthesia machine or carbon dioxide absorber. The inspiratory coupler handles gas from the inspiratory tube, and the expiratory coupler end handles gas from the expiratory coupler.
Both the inspiratory and expiratory tubes function in a similar manner. Anesthesia gas and oxygen are directed into the inspiratory tube, where the gases travel from the machine end of the inspiratory tube to the patient end. The gases are then inhaled by the patient. When the patient exhales, his expiratory gases flow into the expiratory tube, which conveys the gases back to the carbon dioxide absorber. Within the carbon dioxide absorber, carbon dioxide is "scrubbed" from the gases to remove it from the gas stream. The expiratory gas may be then routed back into the inspiratory tube for rebreathing by the patient. Of course, it is often advisable to add oxygen and/or anesthesia gas to the rebreathed expiratory gas, to increase the oxygen and/or anesthesia content of the recycled gas being inhaled by the patient.
Devices which cover the exterior of a breathing circuit are known. For example, Smith U.S. Pat. No. 5,377,670 discloses a casing which surrounds a breathing circuit tube to define an insulating dead air space between the breathing tube and the casing for purposes of temperature retention.
One difficulty encountered with all breathing circuits is that viruses, bacteria and other germs become resident on the breathing circuit during use by a patient. To avoid cross-infection, the breathing circuit should not be used by a second patient without sterilization between uses. To help eliminate this risk of cross infection, the breathing circuit can be designed to be a "single use" breathing circuit that is discarded after a single use. An alternate way to avoid cross infection is to sterilize and autoclave the "re-usable" breathing circuit after each use.
Both of these methods have drawbacks. Autoclaving a breathing circuit after each use can result in substantial labor and processing costs. Although discarding the breathing circuit after a single use is very effective in preventing cross infection, single use circuits can result in additional costs to the hospital.
Another method for dealing with cross infection is to place a filter on the breathing circuit for filtering out bacteria and viruses, thus preventing them from becoming resident within the breathing circuit. Such filters typically act to prohibit such bacteria and viruses from becoming resident on the interior of the breathing circuit. The filter itself, upon which the bacteria and virus have become resident, can then be discarded after single patient use. Through this procedure, the breathing circuit can be reused, although the filter must be either disposed of or re-sterilized.
Although such breathing filters have proven effective in preventing bacteria and viruses from becoming resident on the interior of the inspiratory and expiratory tubes of the breathing circuits, typical filters do nothing to prevent bacteria and viruses from becoming resident on the exterior of the breathing circuit.
Pre-operatively or peri-operatively, blood and other bodily fluids often become discharged or transferred (via the practitioner's hands) from the patient being operated on, to the medical equipment and personnel within the surgical theater. These bodily fluids contain a wide variety of bacteria and viruses that are not visible to the naked eye. If the bodily fluids, and hence the viruses and bacteria, make contact with the exterior of the breathing circuit, they will become resident on the breathing circuit, and thus have the potential to cross-infect another person.
As a goal of modem surgical practice is to provide a substantially "germ free" environment, the presence of such bacteria and viruses on the exterior of the breathing circuit is undesirable, and hampers the ability of the circuit to be reused without sterilization. By preventing bacteria and viruses from becoming resident both on the interior and exterior of the breathing circuit tubes, one would enable a breathing circuit to have the potential to be reused for multiple patients, without incurring a substantial risk of cross infection among patients.
It is therefore an object of the present invention to provide an apparatus for helping to prevent bacteria and viruses from becoming resident on both the interior surfaces and exterior surfaces of an anesthesia breathing circuit.